He just did this work for $120 to satisfy an insurance requirement. 

Hi David - I don't have any suggestions for app based calcs, but if you are familiar/satisfied with the web based desktop version we have here, it should be mobile friendly to use within your phone's web browser.

Acquire a property, live in it as my primary residence (for reals) while I'm rehabbing it, then convert it to STR after I've satisfied the primary residence conditions of the mortgage (usually 1 year). 

It may be a year or more before you find someone suitable, during which time your mailbox money will have dried up.There's also a good chance that you will need to invest additional money to fix up the property to attract the new tenant, who is unlikely to be satisfied with the very customized layout of the last one.

There's always market for short term financing that's not being satisfied by traditional banks.  

She spent about 30 seconds looking around, was satisfied that we were in good shape to start construction, and gave us our approval to officially start.Only problem is that this is now Friday morning, and our grading/excavation guy isn't going to want to start work until Monday.

Just selling a house isn’t going to satisfy a lender to give you another loan.Let us know if we are missing the point here… but cash flow is usually your income, and without it I don’t see a way forward with your plan barring other unmentioned resources. 

This would satisfy your 1031 exchange. 

This is regardless of any contingency, other than perhaps financing, since he couldn’t have completed the deal even if the contingencies had been satisfied.  

It's like a giant monster that is never satisfied.